


THORNS

by Che_Butter



Category: Adventure Time
Genre: (TWISTED!!) Fern the Human (DOM), Body Groping/Dry Humping, Chloroform, Choking, Explicit Language, Explicit Sexual Content, Fan Art, Finn the Human (SUB), Fondling, Humiliation, M/M, Masturbation, Mind Games/Manipulation/Deception, Non-Consensual Bondage, Physical Abuse, Stroking, Torture, Wrestling Match/Struggle, dark themes
Language: English
Status: In-Progress
Published: 2019-07-02
Updated: 2019-07-12
Packaged: 2020-06-02 12:27:37
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Major Character Death, Rape/Non-Con, Underage
Chapters: 3
Words: 8,976
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19441465
Author URL: https://archiveofourown.org/users/Che_Butter/pseuds/Che_Butter
Summary: Fern, known now as “The Green Knight” decides to go against his employer’s wishes and kidnaps Finn in an attempt to get even.But one fantasy leads to another and another, and before long Fern’s immense pent up lust for sexual gratification ends up with Ooo’s future changing in ways no one ever thought possible. Especially Gumbald.Who ever thought Fern could be so kinky and devious behind closed doors?*REQUESTING REVIEWS*





	1. Breaking In and Entering

**Summary for the Chapter:**

> Not everybody enjoys celebrating their birthday. Fern definitely doesn't. He doesn't get a party, can't eat a blasted Finn Cake, deals with a pansy ass piece of gum as an employer, and WORSE OF ALL, has to constantly play second best to Finn. His own Human self! No matter though, Both Finn and Fern's 17th Birthday isn't exactly over yet. Well, not for the green knight anyway.

**Notes for the Chapter:**

> Hi, fellow AO3 writers and readers!
> 
> Here is the first chapter of my Adventure Time Fan Fiction THORNS. So far of all the stories I have written and posted online, this story stands currently as the most graphic and dark. Hence the reason why it has an explicit rating and also why I decided to finish uploading chapters here instead of its original place on Fan Fiction.net. 
> 
> I hope you enjoy reading and find my chapter artwork appealing! Fern is such a handsome thing, isn't he?

Damn that stupid Finn! Damn him! Damn him! Damn him! Fern mentally screamed. It was all his damn fault that all the previous events at The Candy Kingdom earlier happened anyway. Now Fern was in trouble with his employer and all because flipping plan b Finn existed!

The green knight paced around his room. Well, it was kinda a room, if you squinted. It definitely wasn't what one would consider a normal kind of living space but Fern wasn't really allowed to live in one of the castle rooms. So he had a little area outside that was dedicated just for him. A grass hybrid sanctuary if you would like to call it. There was a cluster of trees and high up in their entwined branches was a small treehouse. Nothing like Fern's old one that he had lived in when he was Finn. But it was still pretty cool. He had a bed, a small bathroom, and even a closet. Fern didn't know why he had the bathroom or closet, as he really didn't need them, but was grateful all the more for the Gumbaldians.

He wasn't though grateful for the tongue lashing he got from Gumbald though. Jeez. The guy had a temper! Wasn't candy suppose to be sweet? Fern shook his head at the memory. Note to self, just obey Uncle G's every word or pray to Glob that Gumbald never finds out otherwise. Stupid, stupid Finn! It really was his fault! I mean it was Fern's stinking birthday too!

With a huff, the knight jumped out of the tall tree that he had been calling home the last few weeks. The thud that his boots made when he hit the ground oddly satisfied the teenager. Probably because Fern secretly imagined the thud being Finn's head getting hit by a 2 by 4. It really was all Finn's fault though. Everything that was Finn's was actually Fern's. Why was Fern the bad guy for wanting his life back? His friends back? A fucking Finn Cake?! Why was that so wrong? Why did he get in trouble for attacking Finn? Wasn't that what he was suppose to do? Glob he was confused.

The hybrid found himself walking, his green form casting a rather intimidating shadow when the full moon illuminated him. Silently chuckling at the irony of it all. Literally Fern hated Finn, which was in an essence, himself. Fern hated himself. He hated who he was and he hated who Finn was too. But the thing he really hated the most was the issue with his lower groins. The issue that Finn had never been able to really contain. Yeah, Finn had had sex. But the things Finn had always desired had always just stayed as fantasies. Mostly out of fear and his own inner disgust.

The trees soon cleared, all except one. Fern looked at it with such hate and ummm, longing. The treehouse was a reminder of everything Fern could never be. The life that he could never return to. Fern had come to that understanding when Finn had murdered him with the robotic arm that Princess Bubblegum, Fern's "friend" gave to him awhile back. The demon within him was speaking some sort of dark, sadistic crap at the memory, that made Fern unconsciously reach for his member. Damn Finn! If he wasn't such a pansy, maybe Fern wouldn't be so frustrated!

The teenager knew he had his orders to turn around, to not engage with Bubblegum's champion. But yet something inside of him propelled him forward and strangely enough it wasn't the grass demon. The teen's slender hands touched the tall green grass that blew in the wind. How nice it felt! The treehouse's scratched door opened up rather easily. Stupid, stupid, stupid Finn. The moron almost died earlier! Was he really that ignorant to actually leave the front door unlocked?! Fern in a lot of ways was glad that he wasn't clueless Finn. His human counterpart's clueless nature was rather embarrassing at times.

Fern found himself slowly in the treasure chamber. Mountains of gold, diamonds and a few historic human objects covered the wooden floorboards. All discovered by Finn and Jake on their previous adventures. Ahh, The memories of those less confusing times. When fighting was fun and Fern was just Finn. Not a replica. Not a sword. Not a combination of human flesh and dark grass demon matter. Just Finn the human with his dog brother, Jake, saving Ooo one villain at a time. Those were the times.

The ladder creaked under him as the knight climbed up on top of the roof. It was kinda stupid. Okay, scratch that, it was REALLY stupid. Fern could have easily jumped onto the roof in the first place and saved a step. But something about doing his old human routine just felt right. He climbed in thru a window, again which was stupidly unlocked, and found himself viewing the living room and then the kitchen. Nothing had really changed. The place was still a flipping mess. Looking thru the fridge, Fern found a bunch of freshly made Finn cakes. How he wanted one! Nimble hands quickly grabbed the tray. Knocking over a container of Jake's freshly squeezed orange juice in the process. Fern almost took a bite. Almost. But his grassy reflection reflected from the one side of the medal tray and stopped the reaction all together. Glob, he hated Finn.

It was at that moment, when Fern let his emotions take him completely. He was breaking an order from his superior by being this close to Finn already. Why not just finish the job? With that the grassy human climbed up the pole leading up to the second and third stories of the treehouse. He would finish the job he had started earlier and the Gumbaldian's would thank him. With Finn around, Gumbald's dreams of defeating Bubblegum would always be just a dream. But with Fern taking matters into his own more than capable hands, well, taking The Candy Kingdom would be easy. Yes, they would thank him.

Finn and Jake's sleeping quarters, like everything else in the treehouse, remained unchanged. There was still some dust and dirt on the wooden third story floors. It was always hard lugging a vacuum cleaner up here. Fern willed his boot covered feet forward, Smirking at the pretty form before him becoming more and more clearer with every slow step.

Finn was beautiful. His robotic arm hanging loosely off of the boy's fur coated cot. Long strands of blonde hair gently caressed his delicate face as Fern found himself stroking the human's cheek. The knight's fingers then gently traced his other copy's slender, red pajama covered figure. So soft and smooth.

Snores echoed behind the knight. Fern didn't have to look to know that it was Jake. He didn't have to worry either. Jake the dog could sleep through anything. Literally ANYTHING. One time when he was still Finn, he had been trying to surprise Jake with his own special bacon pancakes recipe and ended up nearing burning the whole treehouse down. If a half in hour of Finn's high pitched adolescent screaming and the intense amount of smoke didn't wake Jake up, then nothing could. Jake's powerful REM sleep was going to be a blessing though for the smirking anti hero but would most certainly be a curse for the hero himself.

The rival Finn watched his replacement for just a few more seconds. Taking careful notice of the blonde's little lips as they exhaled ever so slightly and his long blonde eyelashes fluttering in the obvious sleep created bliss, before pouncing on the unsuspecting beauty sleeping peacefully before him.


	2. Two Finns On a Bed

**Summary for the Chapter:**

> Finn has no idea that his birthday is going to get a hell of a lot worse and it all starts with a very cheeky looking Fern laying overtop his sleeping form. So much for our blonde hero getting a good "knights" rest.

**Notes for the Chapter:**

> Howdy everyone!
> 
> Anyway, I want to send a special thank you out to fellow AO3 writer, pokiemon2013 for sending me such nice feedback, Much appreciated pokiemon2013! 
> 
> Also thank you guys for the 4 kudos THORNS has received and the 82 readers that have so far read this story! It makes me so happy that people are enjoying reading!!  
> So, thank you all so very, very much!!
> 
> Now onto chapter two of THORNS. Where things are about to get interesting between our baby faced demon and our hunky hero......

Finn had been dreaming of the good old days. The days when he was just a carefree kid without a damn worry in the world. It was just him and Jake fighting alongside one another, saving The Candy Kingdom. Finn had wanted Bubblegum so badly back then and then gradually the attraction for her found its way to Flame Princess, who he ended up.....destroying his chances with. 

His dream changed to the events that led up to their breakup. Phoebe should have done more to him than she did. He messed up badly. A punch to his jawline would have even been more than fair given the circumstances. Even though, Finn thought that he had deserved a punch from Phoebe when their relationship ended, he wasn't expecting the Flame Princess to actually knock the air out of him. It actually woke him up.

He groggily opened his eyes and that's when panic struck in. Fern was sitting atop his sweating chest with the most crooked grin that Finn had ever seen on a face. That smirk gave the now fully awake hero chills.

"Hello Finn." The knight whispered. His lips rather close to Finn's ear. "How you been?"

How had he been? All fear nearly gone from the human teen's body in an instant.

Like, what the hell man?! Fern hours prior almost killed him! What kind of damn answer did the grass counterpart except the blonde to give?

"Just dandy, dude. That punch you gave me earlier was a perfect way to show me how much I mean to you." Finn retorted sarcastically, rolling his blue eyes in the process indicating even more of his obvious irritation.

Finn felt Fern tighten up around him in an almost threatening way. The demonic cat slits stared down at the extremely uncomfortable boy with a mixture of cockiness, confidence and…..lust? The last one was new. Then again maybe the hero just was imagining things. Now if only he could imagine Fern vanishing. Now that would at least be something to tell Jake in the morning. If he survived this whole current ordeal. Actually speaking of the boy's dog brother.......

"I wouldn't scream if I were you Finn.” Fern stated in a calm almost bored manner. “We both know that Jake isn’t going to hear you."

Finn closed his eyes, feeling Fern's strong hands around his throat. Damn him! Reading the hero’s mind through the mental link that they once both shared wasn’t fair. Finn hadn’t used the link in ages. He believed strongly that Fern deserved his privacy. Also up until earlier, Finn honestly thought Fern was dead. 

The hero would just have to come up with a different plan. One that obviously didn’t involve him reading Fern’s thoughts because apparently like with everything else, the connection that the two shared once was now officially one sided. Finn even though he knew it was hopeless, tried to once more connect to his alternative self’s mind. But just like earlier at his seventeenth birthday party he was unsuccessful. 

Finn just assumed it was yet another one of Gumbald’s so called “improvements.” But now as he was forced under Fern’s body weight, he truly understood. The sweet little plant boy that the blonde had admired was no more and so was Finn’s mind link. Fern was indeed gone. Replaced by this twisted, vindictive being that held him hostage in intense hatred for some strange reason. 

The other thing the blonde had to avoid doing was screaming, because Finn really wasn’t in the mood to get choked and it seemed that every time the boy would part his lips every so slightly, the hands wrapped around his neck would tighten.

"What do you want Fern?" Finn asked. His voice coming out sounding more like a whine than the unfazed tone he was going for.

The hands traced the blonde's neck in a circular movement. What was he planning? Finn knew that Fern was aware of his robotic arm. I mean it wasn't long ago that the blonde had mistakenly used the weed-wacker setting on the being. It was a mistake then but now, Finn was 100% sure that he wouldn't hesitate to use the same feature in his robotic arm if need be.

Again, the events earlier at his birthday party played in the hero's head. No, he would definitely not pause to use the setting again. Not after the shit that Fern had pulled hours prior. So, then why was the grass knight so relaxed? He was breaking in and entering, and this technically was assault. He couldn't be that stupid.

Both boys stared at one another before Fern let out a rather unnerving laugh. What was the knight planning? Hopefully the grass Finn wasn't reading the blonde's mind because after the hybrid's laugh continued for a good bit longer, the hero was already preparing himself to audio command his arm. He was just waiting for the right moment to strike and the last thing Finn needed was Fern to find out what the hero was patiently waiting for.

"It's my birthday too, Finn." Fern said suddenly, his eyes hungrily looking at his captured prize.

Finn resisted the urge to shudder when his villainous self put his head on his chest. The action caused a cold shock to race through every vein in the blonde's body. Fern's quick movement left Finn temporarily stunned until the said boy remembered the grass creature's hands, which still resided close to his neck. A little bit too close in the human’s personal opinion. 

Fern wasn't much bigger than the hero's physical form. Maybe that was why much to Finn's displeasure, the grass boy laying on his chest felt rather nice. The mortal started to move his arms to hug Fern back, when he found himself held down by one of his attacker's strong hands. The other still rested firmly on the human's windpipe. A warning perhaps? But for what? The only answer Finn received was Fern's terrifying cat eyes glowing up at him as he tried to fight the fiend’s hold. 

"Let me go, dude." The hero started. The human couldn’t shake the feeling of dread that was overtaking him. He really was kicking himself for not using his robot arm when he had the chance. Fern was planning something. Something that made Finn feel nauseous.

"I told you, it's _my_ birthday too, Finn." the knight said. A playful tone laced in his voice as he tightened his grip causing Finn to cry out. So much for being manly.

"And unlike you, I didn't have a party or any friends to celebrate with." With every sentence Fern gripped the mortal's wrists tighter and tighter. The blonde was definitely going to have bruises when this was all said and done.

"What are you doing?" Finn cursed inwardly at his spoken words. There was no hiding his uncomfortability in the sentence. Fern cocked a eyebrow in amusement as Finn’s question.

"I didn't even receive any gifts." The hybrid responded. His voice low and screamed danger. If only the blonde could get away. If only he could somehow wake up Jake!

Before Finn had any time to react the fiend pulled his captive's arms to their sides, pinning them securely underneath his own muscular body. Finn struggled, panic once again filling up his figure.

"But no matter," Fern's mouth was right beside Finn's. The human's breath smelled like peppermint. His blue eyes looked at his captor with fear. Finn wasn't even hiding it now. The realization that spread across the hero's face was a very rare thing. Fern just couldn't resist stroking the mortal's cheek again after seeing such a look. The pale yet flushed cheeks were so soft and warm. Was he as hot on the inside? Only one way to find out.

"I will just give myself a gift." Fern said quickly. His deep voice giving his captive goosebumps at the tone. He was scared yet he was also turned on for some sick reason. Strange. Finn's eyes widened in alarm as Fern mouth crashed onto his own. The hero kicked and bucked wildly. Yet the alternate him held him good and fast. 

The kiss while dry, and mean spirited, was extremely passionate. Which unfortunately, only added to the arousal that the unhappy mortal was trying to ignore. Typical stubborn Finn. The blonde's actions didn't surprise Fern in the least. He was excepting Finn to deny him. It was all part of the game and Finn’s defiance was only making Fern's obvious approval even more noticeable in his tight pants. 

"See? Was that so bad?" Fern taunted. "I just wanted to give the birthday boy a gift because you are just so “special”"

The hero thrashed in the green knight's hold, even after the kiss ended. The said knight just laughed at the silly pathetic attempts. He wasn't even in his complete green knight form and he was still stronger!

"What do you want, Fern?" Finn huffed. Sweat was starting to form on his pale forehead. One look at the human and one could tell that the handsome boy was growing tired.

Fern looked up at the ceiling for a moment. Almost as if he was thinking long and hard about what he in fact wanted. Of course, Fern's mock indecisive gaze was short lived before his eyes returned to Finn's. A devious smile spread across his lips as Finn paled even more.

"I want my gift now."

Suddenly Finn found his mouth covered by one of the knight's hands. It wrapped around the human's shaking head like a gag. Finn screamed but it was gargled. What the hell?! 

A strong sweet smell coated started to coat his nostrils. The teenager had smelled the same scent in Princess Bubblegum's lab before and even had it used on him once or twice in the past when he was PB's test subject. The human literally would have put his head on a silver platter for the candy monarch when he was younger.

It was chloroform. A drug that could do one of two things depending on how it was prepared. It could knock out the person or even worse, it could kill the said individual it was being forced upon. Somehow, Fern's plant body was creating the exact chemical.

Fern wouldn't kill him, would he? The human didn't know anymore and that thought truly terrified the hero. Finn tried to fight back again his assailant. His frantic movements shaking the bed that he was held hostage on so much that the nice, soft, red blanket that he had received as one of his gifts earlier fell in a heap on the floor. It didn't matter. All that ran across Finn's panicked mind, was that he had to get himself out of Fern's grasp before it was too late. Before he either passed out or......

The hero struggled and eventually was rewarded with his pale hand coming loose. The said body part started trying to push Fern's body off of the struggling figure. Fern only made a grunt when the fingers started clawing at the knight's side. It was more annoying than anything else. Especially when the hand gave up digging its fingers into the hybrid's ribs and started trying to punch.

The punches were weak and after the third impact, Fern grabbed with his free hand the flaring arm, as well as Finn's robotic one. One can never be too safe. He wrapped his hand around the slender wrists and once again easily hoisted them above the pretty teenager's head. Pulling Finn's thrashing upper body in an almost sitting position.

Just like before, the sound of the human's wrists being forced against the wooden headboard brought Fern a strange sense of pleasure. That and the muffled cries were music to the assailant's ears. The boy's blasted arm enhancement couldn't do any damage if it couldn't understand what the panicking teenager was saying. Honestly this was working out a lot better than Fern had excepted. 

Finn squirmed violently under his captor's gaze. He couldn't break free. He tried twisting his body, to the point of almost falling off the bed. Yet even so, the human couldn't get Fern off of him and the worst part was his vision was fading.

With the last little bit of strength in his weakening body, Finn got enough momentum in his legs and rolled over onto his side. Fern wasn't excepting the action and like Finn collided on the wooden floorboards. If Finn wasn't so desperate to get away from his attempted kidnapper, the human would have breathed a sigh of relief and maybe thrown in a few witty remarks.

However, even if the thought of being a complete and utter smart-ass ran through the champion of Ooo's head, he had no time to act on it. Finn's success was short lived as the rebel knight just punched Finn in the stomach, for the second time that day, and hopped back onto his form.

This time though grass counterpart did not even bother to hold onto the writhing fighter's hands. The pitiful look in Finn's eyes told Fern that he wouldn't be conscious much longer. What a shame. Fern was enjoying Finn's attempts to fight back. They were cute.

Finn got about 2 letters into Jake's name before the sickeningly sweet smell was back invading his nose. The human's struggles were dying down. His feet and part of his legs getting tangled in the big quilt wasn't helping his predicament either. He couldn't move from under Fern's triumphant look and after a few seconds of Fern's own scent being reapplied forcefully to his face, he passed out.

The seventeen year old's body went limp under Ferns. The grass Finn played with a few strands of the blonde's long hair before carefully rising from the now unconscious hero. Without hesitation, Fern grabbed his enemy's waist and flung him over his shoulder. Finn was so delicate and petite! Why hadn't the plant boy done this earlier?

With a quick smirk at the still snoring Jake, Fern quickly descended down the pole to the first floor of the treehouse. As the front door closed behind him, Fern couldn't help but wonder again how stupid Finn could possibly be to leave the damn entrance door unlocked.....

Oh, well. Like with everything else this was Finn's fault. Not his.


	3. Trapped...and NOT In a Good Way

**Summary for the Chapter:**

> No one likes it when they wake up and can't remember how the hell they got there. But for our blonde hero, waking up is only part of the issue. He's got more "pressing" issues to worry about. The main one being what part he plays in Fern, the green knight's plan.

**Notes for the Chapter:**

> Happy Friday everyone!!
> 
> Here's the next chapter of THORNS for you guys! I went ahead and put everyone's thoughts in italics, in hopes that it might be easier for you guys to read. Also, another heads up! This chapter is extremely dark. But you guys asked for kinky, so I delivered. 
> 
> As always I start the chapter off with saying thank you to all of my readers! THORNS so far has 11 Kudos, 188 Hits and has had 2 individuals kindly send me feedback. Thank you fellow AO3 writers, pokiemon2013, and TrebleCat, for your positive feedback on chapter two. The more feedback and subscriptions I receive (hint, hint), the better a writer I can become.  
> So, thank you both!
> 
> Now, onto the story!!

Fern had found the dungeon by accident months prior on a self created journey that he had hoped would help him find himself. What a load of crap that was! All the blasted waste of time trip did was just irritate him even more. Everything Fern could do, Finn could fucking do better! So, what was the point?

Of course, the dungeon that the young man had come across did in a way assist in helping Fern find something. The teenager had spent quite some time wandering around the abandoned area. His hands touching the dirt and stone walls with such tenderness, almost as if the boy was afraid that the ancient structures keeping him concealed would just collapse right then and there. The place was beautiful in a creepy sort of way. A reminder of an era that had long been forgotten in history. The hybrid had been especially called to one of the large caverns way to the far back of the building. The cave like all the others was dark and gloomy, yet unlike the others housed two huge doors at the entrance. It was there, beside the strange hieroglyphics that Fern decided on luring and trapping his replica in such an area. Finn wouldn’t be able to escape such a predicament and the blonde would lose himself in the process. As for Fern though, he would quickly and happily adjust back to the life that was once his.

That was the thinking then. It was a good plan but the sneaky grass being overlooked a few pointers. He had under thought the obvious. Finn and Fern WERE the Same person. Even if the thought did piss Fern off. Fern had to keep Finn somewhere that he himself, if he were in Finn's helpless predicament, couldn't escape from. Somewhere where Fern’s good alter ego couldn’t use his arm to take out one of the walls. Like he did to the last cave that the teenager had trapped him in.

 _‘Hmmm, choices, choices.’_ The green knight said to himself. _‘Where could I possibly keep you?’_ His eyes gazed back down at the unconscious form he was dragging. Fern could have easily prevented such a matter. The mortal wasn’t heavy in the slightest, and even without Gumbald’s enhancements Fern could easily have continued to carry Finn over his shoulder. However, something about dragging the human thru hallways and hallways of dirt and grime just made the green knight smile. Finn’s red pajamas looked more rust colored in the dark surroundings. While Finn’s hair still looked about the same. Other than a few sticks that were tangled in the boy’s luscious blonde locks of course.

 _‘Damn you. Even when you lose you always end up making me the shadow.’_ Fern scowled under his breath, pulling Finn intently through a puddle that was caused by a small leak in the ceiling. _‘Always the light even when you are being trapped in darkness.’_

Darkness. That was it! With a smirk one last time at Finn, Fern pulled the hero down an even more smaller passageway. He knew exactly where to put his captive. It was a place that Fern had only found once, hence why he didn’t place Finn there the first time. It was too risky at that point. But now? Now, there was literally nothing holding Fern back.

Darkness soon covered the area around the two warriors. Dust coated Fern's mouth as he continued to drag his victim deeper and deeper underground. Memory and sound were Fern's only guides. His sight while still functioning was a bit blurred due to all the dust the two were kicking up. That being said the hybrid never ceased to lift his long fingers from the vastly narrowing wall. This included when his heart skipped a beat after hearing Finn mutter something faintly behind him. It was just a noise, but a reminder to Fern that he had to hurry. The last thing he wanted was for Finn to be up before they got to their final destination.

Of course, like everything else in Fern’s life, he had somehow reached a dead end. The wall in front of him from what he could see looked just like an ordinary wall. Had the green knight taken a wrong turn? Damn! He didn’t have time for this! His long fingers traced the walls frantically beside him. The space was narrow. So narrow that it was hard even moving the fiend’s arms around.

Suddenly Fern’s fingers found the key pad. “Oh, thank Glob.” The grass being said in relief. His free hand easily found the lone sticky button at the top of the wall. Strange and foreign symbols lit up in a wide arrangement of colors. The bright lights made Fern wince ever so slightly at the color’s vibrant hues. Colors, much to Fern’s bewilderment also lined the wall blocking his way. They traced the middle part of the stone until the silhouette of a rectangle appeared. The knight had seen this display before and while he was rushing to get Finn inside, it still made Fern speechless. Yes, Fern didn’t gave a damn about the past anymore, and looked only towards the future. But still he did appreciate the beauty of things that were long created before him.

The door rumbled as it slowly opened. Fern glanced down his toy, his eyes glowing like green embers. This was it. The door shut behind them just as Finn's feet were pulled through.

 _‘Perfect.’_ Fern thought as he scanned the room in contentment. _‘This will be perfect to keep Finn contained in. There is no way that Finn can escape this trap and there is no way that anyone will ever be able to find him.’_ He made another silent pray to whatever cosmic entity was listening, when his eyes finally were able to focus clearly.

The green knight pulled Finn closer towards the middle of the cave. Dropping the human’s leg in sheer disgust when several bugs crawled out from under some rocks that were scattered on the ground. The bugs were small and insignificant to Fern’s plan. But the rocks could be used as a weapon, if Finn needed.

That thinking made Fern nervous. He calmly walked around the cave, picking up rocks that he thought that Finn could possibly use later. The being found two that were definitely too big to be left with the blonde. Fern expertly manifested his axe and sliced the two in pieces.  
He was satisfied only when the rocks were just tiny little pebbles. He found another one that wasn’t as big. But was questionable and just to be safe, dealt that rock the same fate as well.

Content once more with his surrounding, Fern touched one of the walls in wonder. It was much too smooth to climb, much too thick to break through for any mortal being, and by far the best part in Fern’s personal opinion, towered over the two individuals.

Fern stepped back in admiration. The cavern the boys were in really was huge. Honestly Fern didn’t remember just how tall the walls really were. They were probably at least 15 ft in height and curved into one another, creating a hexagon shape. He followed the walls absentmindedly. Quickly noticing one of them had an indent farther up towards where the middle section would be considered. A ledge perhaps? ‘Only one way to find out.’ Fern mused curiously. He willed his body to get taller, enjoying the feeling of returning to his original height as the green knight. The small little area that Fern had seen previously, much to his joy, was indeed a ledge. One that could only be accessible by a being that was closer to at least 10ft. The knight chuckled. His boots firmly resting on the small rocky area for a few moments. Before slowly as to not fall off, maneuvering themselves into a sitting position. Now he would have a front row seat to Finn’s panic. Glob!! This cave was perfect!

Finn would not escape. He couldn’t escape. It just wasn’t possible because Fern didn't know how the hell he could escape if their roles were switched. What irony. That this dungeon in particular would actually be the place where he hid himself. Ironic indeed. A yawn echoed around the room. It bounced off the walls, causing Fern to quickly look down at Finn’s twitching figure. The human was waking up. He tossed and turned under Fern’s watch. Muttering something that sounded like a question. The knight’s legs stopped kicking the empty space as he waited in anticipation.

"Jake?"

Right on que. Fern once more to resist the chuckles that were threatening to overtake him.

"Jake?" The blonde said. Finn slowly tried to rise himself off the cold ground. He could barely see his hands. But he could feel them. Feel the cold medal which was attached to his left arm and the soreness in his right. Ouch. His human arm really hurt.

"Hello? Anybody here?"

The young man walked around, well as much as he could. He used his fingertips as a guide as he traced the smooth walls that he was trapped in. Where was he?

"Well, this is just great!" The frustrated hero said out loud. "Just great!" He allowed himself to slide to the ground with one of the walls supporting his back. Finn felt some relief when His long blonde hair fell in his face. The waist length curls were full of knots and tangles and sticks. Yes, sticks. Fingers reached out to his blonde hair in anger as he attempted to pull the sticks loose. How the hell did he get here? Finn’s mind was just replaying his birthday over and over again. Ice king and the cake, the party, the Gumbaldians, the punch, Fern.

Fern.

Relief turned to fear as all the memories of Fern's strange appearance on his bed started replaying in the teen's mind.

"Fern! Oh Glob!!! I gotta get out of here and warn everybody!"

The human's nails started clawing at his arm enhancement instantly. Anything to turn the device on, so that he could start barking orders to free himself from Fern's obvious trap. It didn’t take much for the hero to put together where he was. He had dreams of places like this since the first time Fern had trapped him here. Finn was being held captive in a cave. He couldn’t see hardly anything but the cold wall that his back was leaning against filled him in.

He had to get out of here! His body was in a cold sweat as his voice changed in his panic. Confusion lined his face much to his watcher's pleasure. Why wasn't Princess Bubblegum's gift working? He had unlocked the arm with his signature password already. Why wasn't it responding to anything he said or did?

"Because I took out the battery while we were still at the treehouse." A deep voice from somewhere higher up on the overlooking wall said. "Man, you really are stupid."

Finn quickly looked over where he heard the sound of something heavy hitting the ground. Yet he could see nothing. It was extremely unnerving.

“Like really, really stupid. I didn’t even have to break anything to get to you because you stupidly left the doors unlocked. Completely idiotic.”

The human forced himself in an upright, standing position, willing his body to move towards the direction of the noise cautiously. Clenching his fists subconsciously with his high hopes that he could use them on Fern. The seventeen year old didn't have to have all of his eyesight to recognize that voice. It sent a chill down the hero’s already cold back.

“Then again, I guess not having brains runs in the family then, doesn’t it?” The voice taunted.

"Where are you Fern?!" He found himself angrily shouting. Bringing Finn’s brother Jake into this made the human’s blood boil. “And don’t you dare talk bad about my brother! He has nothing to do with this!” He screeched.

No response. "Show yourself, you coward!" An insane cackle behind Finn made him turn around. He charged at the sound, his hands prepared to come in contact with the knight's face. Only there was nothing. Nothing but a wall. Finn cried out in surprise. Where was he?

“You’re right, Jake is your brother.” Fern laughed maniacally somewhere behind him. “Stupid follows stupid, after-all.”

"Oooh!! You are going to get it now, Fern!" The human yelled imaging the satisfaction of hitting Fern. Only to be greatly disappointed when his fist collided with air. This was ridiculous!

"Damn it Fern!! Come and fight me!"

"As you wish." A seductive voice once more behind Finn whispered.

The human wasn't able to even turn around before a foot collided with his back, knocking him to the cold ground. Laughter rang out as Finn felt something jump on him. Instinct kicked in as Finn punched his attacker. This time pleasingly punching Fern's chest instead of air. The knight retaliated with a punch to Finn's jaw. This wasn't a game for Fern, the human realized as blood started pouring out of his nose. Fern was dealing blows that could seriously be damaging. The blonde used his momentum to push his grassy self off of him. He jumped on the spot that Fern once was and in his dismay felt only air.

Laughter echoed around Finn. Before another punch was landed on Finn's cheek. Then another on his side. As quickly as the human tried to fight back, he wasn't fast enough to keep up with Fern's quick movements.

Continuous slaps and punches befell the bleeding blonde. Finn couldn't fight back. It was unfair. He couldn't really see his opponent and it was pretty hard for his human ears to hear him as well. The green knight was just playing with him. A punch to the stomach caused the hero to buckle over coughing up blood.

"And to think that I wanted to take your place."

Finn suddenly felt himself colliding with the floor. Blood ran down his arm. He tried to get up but Fern kicked him hard in the ribs as a reward for his efforts. The loud crack made Fern smirk more.

“You are pathetic.”

The human tried again to get up. He was resorting to crawling at this point. Finn had no idea where the next strike would come from and was just desperately trying to find a place to hide. His fingers like earlier were his only guide as he mentally counted his steps.

“Weak.”

He only got to 5 before, Fern grabbed his long yellow hair and forced him to his feet. Finn's pain filled shriek sent pleasurable shivers down Fern's very being. The hero roared in rage as he felt himself being dragged.

“Vulnerable.”

Finn twisted as Fern's hand gripped his blonde hair tighter. Bubblegum's champion's hands instantly went to try to pry Fern's hand off of his locks. Fern only pulled tighter. Pulling Finn's head up higher and higher.

“You are dispensable Finn. Just a washed up hero that everyone takes advantage off.”

"Nooo! Fern! Stop! You need to let me go! This is wrong and you know it" Finn yelled. “I know there is good in you.”

"Of course it’s wrong!!!” Fern laughed. “But that's precisely why I am doing it. Because I am done being you. I am done being weak.”

“You are wrong.” Finn whimpered. His body struggled in Fern’s hold, desperate to release itself from the grass being’s tight grip. One of the mortal’s hands found Fern’s face. The green knight only snickered before biting the fingers that were trying to claw at his lips and nose.

“Am I?” The knight questioned venomously. “The only reason you think that there is good in me, is because I was once you. Because your life was once mine, you still think of me as you, just like YOUR friends. I am not you. I am stronger, I am faster and above all, I am just better.”

Finn felt Fern’s voice in his ear. “So please take my old human life, because the truth is, that nobody likes you Finn. No body cares. You are just a puppet in Bubblegum and everyone else’s plans and you will die as such. A useless pawn such as yourself just isn’t worth the time to love.”

“You are wrong!” Finn cried out in anguish. “People care about me. I have friends that love me and care about what I have to say. They care about you too, Fern! My friends are your friends!”

Fern laughed even harder. “What “friends”? Are you referring to the one that called me “demon” or the one that gave you, my replacement, a robotic arm to kill me? Oh, Finn. You really are stupid. Those are your so called “friends.” Not mine.”

“Stop this Fern Please!!” The blonde yelled out. The pressure from Fern’s firm hold was giving the hero a massive migraine. He was having trouble swallowing in the angle that he was in and the pain was bringing tears to his blue eyes. “You can’t do this to me!”

“Is that so?” Fern mocked deviously. “Well then, I guess I can't do this either!"

Finn's hair was suddenly tightly looped it around the bleeding warrior's neck. Finn immediately gasped at the sudden reaction. What the fuck? He kicked out desperate to get the attacker off of him. His body struggled as his airway was slowly becoming more and more constricted. Now he really couldn't breathe! Fern was going to kill him.

"Glob, you really are the most pathetic thing I think I have ever seen."

Finn's hands clawed into his hair. Was he trying to find Fern's tightly gripped fingers? If so, he was going in the complete wrong direction. It was impossible though to reach Fern's grasp. Unless of course, Finn could somehow hyperextended his arm to reach the back of his neck. Fern just laughed at the attempts that Finn was making to free himself. Trying to fight back against Fern's vice like grip, Finn kicked and squirmed, as he was slowly strangled. The human’s body convulsed so much in its peril that a few times Fern felt his hand loosen ever so slightly. It was amusing to see how determined Finn was to escape. The human, twice even tried to fall back into Fern, in hopes that maybe it would trip him. Honestly it was cute in Fern’s opinion. Really cute.

It was for that reason the knight decided he just had to explore Finn's spasming figure. With his free hand, Fern slowly caressed the body trapped against him. His muscular chest could be felt through the torn pajamas. Finn bucked at the response. Shaking his head in denial at the unwanted touch. Of course this defiant action only made Fern grope his slowly strangled victim more. The blonde was warm. He was sweaty too. Finn's struggles were slowing down as the hybrid started skimming over the massive bulge in Finn's onesie. The lower half of the sleepwear was also torn terribly. But it could use some more cuts in Fern's mindset. It was then that Fern also noticed that Finn had stopped kicking his ankles. A gurgled cry was the only response the grass creature received after the realization. Fern could very easily kill him. How easy it would be. A drop of water leaked onto Fern's exploring arm. It was drool. Finn's drool. A few more seconds and the replica Finn would be dead.

Nope, Finn wasn't getting off that easy.

Gently Fern unwound Finn's hair from his pale neck. A weak punch suddenly found its way to the knight's ribs. The hero dropped to the floor, coughing and hacking up a storm.

"Why?" Finn finally choked out. His body trembled as he felt Fern crouch down beside him. Hands grabbed his one shoulder at the question. If Finn squinted he could see the fiend now. Tears streamed down Finn's face, as the knight gently cupped the hero's chin forcing his terrified victim to look at him.

"Because Finn, I absolutely hate you."

The knight's hand was suddenly sticky. He grabbed Finn's hand and pulled them sharply behind his back. The hero weakly struggled against the action. The sticky substance was wrapped 5 different times around Finn's shaking wrists. It was just like webbing. Finn tried to pull free but was unsuccessful.

"Why Fern?" Blood mixed with tears as Finn tried to thrash. He was going anywhere. But even though he was exhausted he had to try. "Why are you doing this?

The knight said nothing. He just grabbed the fearful hostage's ankles and began wrapping them up as well.

"Please Fern. Please let me go."

Fern only gazed up at his human half. How pretty. Especially since Finn still had the the obvious arousal that he had earlier. The impressive bulge was still there.

For a moment, Finn thought his pleading actually reached Fern. His other half's hands slowly stroked Finn's cheeks in a very soothing way. Finn closed his eyes at the touch. He was scared but this feeling was overriding his weariness. That was until, Finn felt the webbing starting to form once more in Ferns palms.

"No, please don't do this Fern! Noomonnnmlopokjhgb!"

Finn's pretty pleas grew more and more quiet as Fern wrapped layer and layer of the thick webbing around his face. Careful to not block Finn's nose as the hero continued to weakly struggle.

"I don't want to hear your pathetic cries Finn.” You are mine to do whatever the hell I want with." Fern said threateningly. His hands held his victim’s head forcing the bruised and bloodied face to look back. Fern’s demonic slits were staring straight into Finn’s sky blue orbs with such hatred that the mortal couldn’t find the strength to look away.

"No one is ever going to find you, Finn. So I suggest that you remember what I just said."

Finn screamed as Fern forced him back down on the ground. With Fern no longer holding his head still, the hero closed his eyes as the being drew his grassy sword. _‘Just make it quick.’_ He prayed inwardly. _‘Glob, Prismo, The Cosmic Owl, Gob, ANYONE, Please just make it quick.’_

The blade came down but not where Finn was excepting. His eyes opened in shock as cold air suddenly hit his near nude stomach. What was worse was the blonde’s red pajamas were being cut more. Finn tried to turn over but Fern's hand held his stomach still. Tears rolled down his face in horror as the knight continued to tear more and more of the clothing. Soon his white boxers were the only things hiding the human’s shamefully arousal.

"What's wrong Finn? I thought being kidnapped, tied up and being raped was one of your fantasies?"

Finn tried to say something in response but his words came out illegible. His eyebrows furrowed at the sound of his muffled cries. Oh Glob! He really did sound pathetic.

"Sorry Finn, I can't hear you." Fern taunted cruelly, his fingers tracing the webbing around the boy’s pale face. "You got something right here, just resting on your face."

The human screamed against the enemy that was holding him steady. He twisted his body this way and that, hoping to at least cause some sort of difficulty for Fern, who was getting closer and closer to Finn's hardening member.

"That’s gotta be frustrating. Here Finn, let me help you with that." The grass knight said darkly. His smile reminded Finn of one of the vampires that he had helped Marceline hunt a few years back. The hero screamed in absolute terror as the slap echoed in the room. Finn’s cheek stung terribly even after Fern’s hand left.

"Oops, sorry my hand slipped. Let me try that again.”

Finn closed his eyes as Fern’s hand smacked his other cheek in the same fashion. More tears rolled down the captive’s face.

“Oh, what’s wrong? Am i being too rough with you, hero? I thought you liked pain? If its too much why don’t you just tell me to stop then?”

Finn slowly opened his eyes to see Fern perched atop his body.

“Well, go on. Tell me to stop.” The knight said. The cheeky grin was still plastered on his face as Finn shook with fright.

“Hmmm, I was so sure that you had something you wanted to say. You know with all that struggling you were doing." Fern cooed menacingly. He watched in sickening amusement as Finn flinched when his hand got close to his face. “But, silly me. It must have just been my imagination.”

Very gently, the grass knight stroked his captured prize’s cheek, admiring the mark of his hand that was on both sides. Finn stayed perfectly still at the gentle touch, mostly out of fear that he would get slapped again if he did anything but. Finn forced his body to remain still even when he felt Fern's hand slide under his boxers and grab his dick. The helpless seventeen year old felt his blood turn cold at the unwanted touch.

"Or maybe, just maybe, I am just not talking to the right head."

Fern giggled at his toy's appalled reaction. Both the boys knew that this was a sexual desire that they both yearned for. Though they really had desired it from Flame Princess during their too short boyfriend/girlfriend relationship.

"It's funny Finn." The knight said out loud concentrating on moving his hands up and down Finn’s shaft in steady, forceful motions. The blonde closed his eyes at the growing pressure. His body was now fighting him.

"The only person who will ever truly be able to sexually satisfy you will be yourself."

Finn started making moaning noises as Fern started to go faster with his strokes. Finn's unwilling pleasure was building up. The knight watched his tied up submissive twitch indicating his growing need. Finn's juices were leaking. Wide eyes looked up at Fern's pleadingly.

"But sadly, you really aren’t my type."

The moment Fern's hand slide out from Finn's boxers, Finn's body panicked. The fiend watched with lust as his human counterpart fought his restraints harder than ever before. He shook his head in outrage at the loss of contact. Fern circled his suffering self like a vulture. Appearing only for a moment in Finn's vision before vanishing again. The mortal rolled over on his stomach, attempting to dry hump the ground. Anything to release the stinging pressure in his groin. Fern watched with glee as the blonde's hands moved frantically in their webbing. The human needed to release and bad! Finn's frustrated screams intensified as his ordeal continued. The hero was stuck in the increasingly painful cycle of incomplete pleasure. He couldn’t get himself there without Fern’s help, but the knight had disappeared. Leaving Finn’s excited body's tremors to grow more and more intense. The human was ballistic, shaking his head and rolling around almost like a cat in heat.

Finn’s captor decided to transform back into his original green knight form and sit back on the ledge. He really did have a front row seat to the beautiful display before him. Finn was desperate, anyone could tell that. But being able to actually hear the said hero’s panicked thoughts was the much needed commentary for the show that he was unknowingly putting on.

"Oh Finn, if only you could free yourself, then maybe you could do this."

The wounded warrior rolled over on his side. His eyes scanning for Fern's lean form. _‘Where are you Fern?’_ His mind wondered. His thinking was scattered, thoughts and desires that he had pushed down so many years prior were coming to straight to the front part of his brain. He couldn’t concentrate. He couldn’t fight the feelings that were bubbling over. His brain could only scream out Fern’s name over and over again.

"Up here, hero." The green knight answered loudly. His voice sounding distant from Finn’s location. The hero wasted no time in once more searching for Fern. He followed his intuition about the wall closest to him. He squinted his eyes and looked up, only for his blue eyes to widen in shock as he watched Fern stroking himself repeatedly. His sitting form arched as he continued to stimulate his own organ.

"Oooooh, ooooh, ooooooh…oh Finn, you don't know what you are missing." The knight on the ledge stated. His body panted as his own orgasm grew. Finn could only watch as his more devious self got closer and closer to climax. Fern's movements were becoming more faster, yet his eyes never closed. They were fixated on watching the pitiful display before  
him.

The human thrashed in his bonds. He needed Fern's help! Really bad! He bucked at the wall, praying that Fern would take pity on him.

"Oh Finn, You poor pathetic thing. I would help you, I really would, but you wanted my life as a hero, so feel my frustrations" The green knight said in between pants. A pleasure filled smile was evident on Fern's face. His voice was changing to a higher pitch and it was only because of the Finn's rather erotic actions.

“Feel….every…..single…..ONE!!”

The tied up hero squirmed relentless as Fern's pleasurable scream filled the cave. Damn him! Fern got there. Finn paused his frantic kicks and forced himself in a sitting position. A quiet yes, echoed across the wall and then silence coated the room. Did Fern pass out?

Nope. Not even close. Hands suddenly gripped Finn's shoulder blades from behind. Finn's need to release was still the only thing on his mind. With the new touch, Finn attempt to take advantage of it. He wiggled against Fern's grip, using his back to weakly attempt to dry hump his captor. Fern laughed a content little laugh at the futile attempt.

"I said feel my frustrations Finn." Fern said quickly right before landing a hard slap to the back of Finn’s head. The blonde fell back to the ground at the impact. He made no movement when Fern walked around to face him head on. "That means all of them Finn. Every single one."

Fern crouched down to gaze at the sight before him. His fingers cupped his alternate self’s chin delicately once more as he stared into Finn’s hard eyes. “Such a look doesn’t suit you Finn. What would your “friends” say?” The knight whispered. “What would your princess say? Or Jake? Would they even notice something like that?”

Finn moved his head around, hoping to get Fern to let go. The green knight only tightened his grip, causing a flash of pain to momentarily appear on the blonde’s face.

“Let’s play a game Finn.” Fern asked, his tone growing more sarcastic as he continued. ”You said earlier that your “friends” care about you? That they “love” you and “value” your opinions?"

Fern’s hand suddenly shoved the bloodied Finn face first into one of the walls. The hero fell backwards gazing up in panic at the familiar pale face smirking before him. His own.

"Well then, Let's just see how well your friends really know you. Let's see if they can spot the difference." The blonde Fern laughed, placing a small kiss on the struggling hero’s forehead. "See you when I feel like it Finn. Enjoy your fantasy."

Muttered cries only made Fern smile wider as he vanished from Finn’s sight completely. With one last peek at Finn’s animalistic thrashing, Fern exited the room leaving the hero stuck in a cave cavern where he belonged and should have stayed to begin with.

**Author's Note:**

> Hi Che_Butter here again!
> 
> Like all the other times that I have posted new chapters here on AO3, I simply ask that if you enjoyed reading "THORNS" to please LIKE, give KUDOS, BOOKMARK, SUBSCRIBE, and/or kindly send me a COMMENT. 
> 
> Your feedback as always is greatly appreciated and with this story in particular, greatly needed! 
> 
> Thank you so much for reading!!!!


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